If you're hoping to get lost in the rain on your romantic getaway, take a look at these details about year-round temperatures in Valentia Island: The hottest months are usually July and August, with an average temperature of 15°C, while the coldest months are February and March, with an average of 8°C. The rainiest months in Valentia Island are November, December, October and January, with each month seeing an average of 193 mm of rainfall.